Re: Understanding integer_cst

[Ian Lance Taylor <ian at airs dot com>]

<Primrose.Mbanefo@Infineon.com> writes:

> I do not understand the gcc internal documentation on the integer_cst
> expression trees.
> An expression is given to calculate the value of the constant:
> 
> ( (TREE_INT_CST_HIGH(e) << HOST_BITS_PER_WIDE_INT)
> + TREE_INT_CST_LOW(e))
> 
> Using the expression, what is wrong in the following example:
> 
> Example
> -----------
> Given integer = 5
> HOST_BITS_PER_WIDE_INT = 4 //just an example
> HOST_WIDE_INT is a type for which the integers are
> HOST_BITS_PER_WIDE_INT bits long.
> 
> Binary representation of given integer is 0|1|0|1
> TREE_INT_CST_HIGH = 0|0|0|1
> TREE_INT_CST_LOW = 0|0|0|1
> -----------
> 
> This definitely does not yield 5 if I apply that expression, so, I
> imagine there is something wrong somewhere.
> If it does, then maybe I did not understand the expression?
> 
> Could anybody please tell me where my thinking went wrong?

Why do you think TREE_INT_CST_HIGH would be 0|0|0|1 in your example?

I would expect

TREE_INT_CST_HIGH = 0|0|0|0
TREE_INT_CST_LOW  = 0|1|0|1

Ian